In wireless communication networks, for example a Universal Mobile Telecommunications System (UMTS), communication channels may be created between: a mobile communications device for providing access to network services over radio communications channels; a Radio Access Network (RAN) comprising at least one radio base transceiver station for sending and receiving information over the communication channels and at least one radio network controller for controlling which communication channel over which radio base transceiver station a mobile communications device communicates and for routing the communications traffic; a core network comprising network nodes for providing network control features, such as billing and authentication, and routing communications traffic to and from the appropriate RAN and to and from other networks; and other networks, such as either a Public Switched Telephone Network (PSTN) or a Packet Data Network (PDN), for routing communications traffic to and from the core network. A mobile communications device may transition between base transceiver stations supported by the same radio network controller according to signal strength measurements received from each radio base transceiver station. A transition between radio base transceiver stations supported by the same radio network controller and further supported by the same core network only requires a radio interface update, and an interface update between the RNC and base transceiver station. However, a transition between radio network controllers supported by different core network requires a radio interface update, an interface update between the RNC and the base transceiver station, an interface update between the RNC and the core network; and a transition between core networks requires the additional interface update between the core network and either the PSTN or PDN.
When a mobile communications device transitions between RNC, the update is referred to a Routing Area Update (RAU). When a mobile communications device transitions between core networks, the update is referred to as a Location Area Update (LAU). The RAU and LAU require a much greater volume of signaling over the radio link than the interface update required when the mobile communications device transitions between base transceiver stations supported by the same radio network controller. Therefore, considering the limited resources and sensitive nature of the radio link, the interface updates required when transitioning between RNC and the core networks should be well controlled so as to prevent unnecessary power consumption and signaling over the radio interface. Because this occurs when the mobile communications device transitions between base transceiver stations supported by different RAN or core network, there is a potential the position of the mobile communications device and radio link conditions may result in frequent and unnecessary updates. This uncontrolled frequency can cause excess power consumption from the mobile communications device and excess traffic over the radio interface.
In order to mitigate excessive LAU and RAU, standard specification 3GPP 05.08 requires that a signal level from a serving base transceiver station compared against a signal level from an adjacent base transceiver station should be adjusted by a predetermined margin value in the case of a LAU or RAU. Adjusting the reference signal may in some circumstances prevent unnecessary updates from occurring, and, therefore, help reduce power consumption and improve radio link efficiency. For example, adjusting the reference signal may help prevent a mobile communications device positioned within an area in the network between two network cells served by two different radio base transceiver stations under certain propagation characteristics from unnecessarily switching between the two cells. However, due to the sensitivity of radio channels and therefore the unpredictable nature of radio channels, the same position at a different time may be under different propagation characteristics, or another position defined by different propagation characteristics, may not respond as well to the same adjusted value. Therefore, there is a need to provide an improved method and of adjusting the reference signal level in order to mitigate excessive network updates.